package com.example.demo;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.stream.ChunkedWriteHandler;

public class WebSocketServer {
    private final int port;

    public WebSocketServer(int port) {
        this.port = port;
    }

    public void run() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<Channel>() {
                        @Override
                        protected void initChannel(Channel ch) throws Exception {
                            ch.pipeline().addLast(new HttpServerCodec());
                            ch.pipeline().addLast(new ChunkedWriteHandler());
                            ch.pipeline().addLast(new HttpObjectAggregator(8192));
                            ch.pipeline().addLast(new WebSocketServerProtocolHandler("/websocket"));
                            ch.pipeline().addLast(new WebSocketServerHandler());
                        }
                    });

            ChannelFuture f = b.bind(port).sync();
            System.out.printf("websocket start port: " + port);
            f.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    private static class WebSocketServerHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
            System.out.println("Received message: " + msg.text());
            ctx.writeAndFlush(new TextWebSocketFrame("Hello, client!"));
        }
    }
}
